The answer I kept seeing from pro-renewable/anti-nuclear people is that banning fossil fuels is unrealistic and impossible. Battery is a tiny part of a tiny part when solar/wind is not producing, as can be seen in sites that provide real time data from EU.
Take a random country in EU. Look at how much energy is produced by wind at peak. Compare it to the lowest lowest point, remove nuclear and hydro, and you get how much fossil fuels that country use at peak. For most countries that is natural gas or coal and it matches wind production almost (only almost as natural gas is a bit more expensive than peak wind, as peak wind can even get negative in purchasing price).
There is also numbers on what power plants countries are currently building. The top one: natural gas power plants. Second one, wind. The power plants we build today is what will produce power tomorrow, and the vector of where investment and constructions is being put is in favor of more natural gas, not less. Nuclear is in many places being replaced by natural gas.
But to get back on track, lets have this ban of fossil fuels in energy and heating. I wish it would happen. It would be great for the environment, force an answer with money on the table on question if nuclear is cheaper than battery, and finally distance the renewable movement away from natural gas. The Northerly regions are not really a big coal/gas users anyway because they also tend to have mountains, rivers, and few people. Hydro will work perfectly fine as long the energy does need to go to southern regions.
To put it simply: countries need to stop building natural gas powers plants and put those investments into battery or nuclear. That is the progress bar for a completely renewable energy grid. As far as I can read it stand right now at almost 0%.